School of Public Health
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Note: Prior to July 1, 2007, the School of Public Health was named the College of Health & Human Performance.
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Item FUNCTIONAL CONNECTIVITY PATTERNS ASSOCIATED WITH AGING, PHYSICAL ACTIVITY, AND GENETIC RISK FOR ALZHEIMER’S DISEASE IN HEALTHY HUMAN BRAIN NETWORKS.(2017) Chirles, Theresa Jeanne; Smith, Carson J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Leisure time physical activity (PA) and exercise training help to improve and maintain cognitive function in healthy older adults and in adults with the APOE-ε4 allele, a genetic risk for Alzheimer’s Disease (AD). Earlier work finding increased functional connectivity in the Default Mode Network (DMN) after a 12-week walking intervention in 16 older adults with mild cognitive impairment is presented in Chapter 3. The primary dissertation study investigating differences in brain function depending on PA level and genetic risk for AD prior to changes in cognition is presented in Chapters 4-6. Useable resting state and anatomical MRI scans were collected from 69 healthy adults (22-51 years) as well as saliva for APOE genotyping (carriers defined as homozygotes or heterozygotes of the ɛ4 allele) and responses to the Paffenbarger Physical Activity Questionnaire (High PA >1500 kcal, Low PA <1500 kcal per week). The following network measures of functional connectivity were calculated: global efficiency; node strength of Default Mode Network (DMN) and Fronto-Parietal Network (FPN) hubs and hippocampal subsections; and long-range connectivity of the medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) in the DMN. Multiple linear regression analysis revealed statistically significant results for the long-range connectivity of the left PCC, a prominent hub of the DMN, and left mPFC. The differences in projected trajectories of the connectivity are potentially reflective of the compensatory time-course in our participants based on interactions of PA level and APOE status. The Low PA non-carriers had a positive slope indicating increased connectivity with age while carriers and non-carriers in the High PA category had horizontal aging trajectories. PA is associated with cognitive reserve (CR), a term describing the protection and adaptation of cognitive processes through neural efficiency and compensation mechanisms, and it is possible the Low PA non-carriers exhibited compensatory increases in connectivity of the left mPFC-PCC earlier than High PA study participants due to lower levels of CR. The promising findings that rs-fMRI can be used as an early detection of brain changes sensitive to PA levels and APOE-ɛ4 status are critical to the research and treatment of AD.Item Variability in Cognitive Performance and Learning in Younger and Older Adults Explained by Cardiovascular Fitness, Physical Activity, and APOE Genotype(2013) Kayes, Maureen K.; Hatfield, Bradley D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation investigated the association of physical activity with cognition in two cross-sectional studies. Physical activity has been positively associated with cognitive function, and in older adult populations has shown an additional benefit for carriers of the ApoE- å4 allele. Cognitive training has also revealed a benefit for improved cognitive performance. Questions remain, however, about the interaction of these factors in their relation with cognition. One study addressed the relationship between physical activity and cognitive performance during executive function and working memory challenges in adults ages 50-70, and the other explored the role that physical activity plays in learning in adults ages 22-50 undergoing an online cognitive training intervention. In both studies, regard for influence of the ApoE genotype was considered, and the concept of specificity of physical activity was explored through employment of measures of both cardiovascular fitness and weekly physical activity kilocalorie expenditure. The study of older adults revealed that performance on a working-memory task was positively related to weekly kilocalorie expenditure in APOE-å4 carriers, with no such benefit for non-carriers during a moderate challenge condition of the task, while a positive relationship was revealed for both å4 carriers and non-carriers during a more challenging condition, but the magnitude of the relationship was greater in å4 carriers. The study of younger adults revealed no transfer benefits for cognitive training; however, cardiovascular fitness was positively related to performance after the intervention on a transfer task of proactive interference, and a positive trend was also found for cardiovascular fitness on a divided-attention language vocabulary learning task. No association was observed with regard to APOE-å4 genotype for any post-intervention task or learning transfer challenge. Taken together, these studies reveal that physical activity is associated with improved cognition in younger and older adults alike, but with specificity as to volume or intensity of physical activity mediating the relationship, cognitive processes benefited, and the role that the APOE-å4 genotype plays.Item The Relationship Between Exercise and Cognitive Function: Is It Altered by APOE Genotype?(2006-12-11) Conery, Ryan; Hatfield, Brad D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The risk of minor cognitive decline and dementia increases with advancing age. Thus, as the average lifespan of humans continues to rise the number of people that are affected by dementia will rapidly increase. Dementia is described as multiple cognitive deficits that adversely impact activities of daily living. Lifestyle behaviors may prove critical in delaying or preventing the onset of cognitive decline and dementia. Specifically, exercise has been shown to decrease reaction time, improve executive function, and maintain performance on gross measures of cognitive ability in an aging population. Further, physical activity becomes even more important when the genetic susceptibility for dementia rises. Apolipoprotein (APOE) e4 is one such risk factor and is associated with the development of Alzheimer's disease (AD). Severe memory loss is one defining symptom of AD and greatly reduces quality of life for afflicted individuals. The purpose of this investigation is to determine the specific behavioral impact of physical activity on those who are genetically at risk for AD compared to those who are not. Sixty cognitively normal individuals between 50 - 70 years old were assessed on medical history, gross cognitive function, physical activity, memory performance (Sternberg memory task), executive control function (Eriksen flanker task), and finally APOE genotype. Using hierarchical regression techniques, memory and executive function scores were regressed on age, education, genotype, physical activity, and the interaction between genotype and physical activity. Analysis revealed that on the more difficult conditions of the memory task as physical activity level increased, reaction time significantly decreased for APOE e4 carriers. No such relationship existed for noncarriers. These results imply, compared with other cognitive challenges, physical activity serves a protective role for maintaining memory, particularly in those who are at a genetic risk for developing dementia.Item EXERCISE BEHAVIOR AND MAINTENANCE OF CEREBRAL CORTICAL ACTIVITY DURING COGNITIVE CHALLENGE IN MIDDLE-AGED MEN AND WOMEN GENETICALLY AT RISK FOR DEMENTIA: A MEGNETOENCEPHALOGRAPHIC STUDY(2005-04-20) Deeny, Sean Patrick; Hatfield, Brad D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Exercise is known to protect and enhance cognitive function in normal aging through increased blood flow and upregulation of neurotrophic factors in the brain. One recent study suggests that carriers of a known genetic risk factor for Alzheimer's disease (AD), the apolipoprotein E (APOE) E4 allele, may exhibit a more profound benefit of exercise on neurocognitive function relative to non-E4 carriers. Brain imaging studies in cognitively normal, middle-aged E4 carriers have revealed deficits in temporal and parietal cortical function even in the absence of clinical symptoms of dementia. As exercise has been shown to protect these regions in normal aging, and even enhance cortical functioning, the current study employs magnetoencephalographic (MEG) measures of cortical activation during the Ericksen flanker task and the Sternberg working memory task to examine whether highly physically active 50-70 year old E4 carriers and non-carriers, who are free from dementia, exhibit greater cortical activation in task-related regions relative to their low-active counterparts. The results revealed that high-active participants, regardless of genotype, exhibited greater activation on the Ericksen flanker task in the right frontal and right temporal regions relative to low-active participants, while performing similarly on accuracy and reaction time (RT). On the Sternberg working memory task high-active E4 carriers exhibited greater activation than low-active E4 carriers in the right temporal region, while being undifferentiated from both the high-active and low-active non-E4 carriers. This effect was most pronounced in the 150-200 ms post-stimulus time window. All groups performed similarly on accuracy and RT. The results suggest that high-resolution brain imaging methods are sensitive to differences in brain function in populations at different genetic risk for dementia prior to any signs of clinical impairment. Furthermore, the relationships between physical activity and brain function are measurable and distinguishable between groups of different genetic susceptibility on tasks and brain regions specific to AD-related neurocognitive decline. The findings support the notion that populations genetically at risk for dementia who remain sedentary may be at greater risk for decline in brain function relative to those who are physically active.